null character

i try to export data do external application from Autocad

i have one problem

i cannot create proper null character for that file

i need null character for determine end of string in that file

function

(write-line (strcat "text" (chr 256)))

doesn't create null sign on the end of line

attached file i want to create (please open it by notepad++ to see null character)

is it possible to create such a file by lisp?

null_charakter.txt

Try the following

[color=GREEN];; Null Character Example by Lee Mac 2014-01-12[/color]
([color=BLUE]defun[/color] nullchartest ( str txt [color=BLUE]/[/color] fso stm )
   ([color=BLUE]if[/color] ([color=BLUE]setq[/color] fso ([color=BLUE]vlax-create-object[/color] [color=MAROON]"scripting.filesystemobject"[/color]))
       ([color=BLUE]progn[/color]
           ([color=BLUE]vl-catch-all-apply[/color]
              '([color=BLUE]lambda[/color] ( )
                   ([color=BLUE]setq[/color] stm ([color=BLUE]vlax-invoke[/color] fso 'createtextfile txt -1 0))
                   ([color=BLUE]vlax-invoke[/color] stm 'write ([color=BLUE]strcat[/color] str ([color=BLUE]chr[/color] 256)))
                   ([color=BLUE]vlax-invoke[/color] stm '[color=BLUE]close[/color])
               )
           )
           ([color=BLUE]if[/color] ([color=BLUE]=[/color] 'vla-object ([color=BLUE]type[/color] stm))
               ([color=BLUE]vlax-release-object[/color] stm)
           )
           ([color=BLUE]if[/color] ([color=BLUE]=[/color] 'vla-object ([color=BLUE]type[/color] fso))
               ([color=BLUE]vlax-release-object[/color] fso)
           )
           ([color=BLUE]findfile[/color] txt)
       )
   )
)
([color=BLUE]vl-load-com[/color]) ([color=BLUE]princ[/color])

Test program:

([color=BLUE]defun[/color] c:test ( )
   (nullchartest [color=MAROON]"line-text"[/color] ([color=BLUE]vl-filename-mktemp[/color] [color=MAROON]"test"[/color] ([color=BLUE]getvar[/color] 'dwgprefix) [color=MAROON]".txt"[/color]))
)

When you write a normal line of text if you hex dump it it will actually have two codes as end of string OD & OA this is carriage return & line feed. Can you not check for these codes if your reading the file like a database and 1 character at a time. If I remember correct is (chr 13)

Try the following

[color=GREEN];; Null Character Example by Lee Mac 2014-01-12[/color]
([color=BLUE]defun[/color] nullchartest ( str txt [color=BLUE]/[/color] fso stm )
   ([color=BLUE]if[/color] ([color=BLUE]setq[/color] fso ([color=BLUE]vlax-create-object[/color] [color=MAROON]"scripting.filesystemobject"[/color]))
       ([color=BLUE]progn[/color]
           ([color=BLUE]vl-catch-all-apply[/color]
              '([color=BLUE]lambda[/color] ( )
                   ([color=BLUE]setq[/color] stm ([color=BLUE]vlax-invoke[/color] fso 'createtextfile txt -1 0))
                   ([color=BLUE]vlax-invoke[/color] stm 'write ([color=BLUE]strcat[/color] str ([color=BLUE]chr[/color] 256)))
                   ([color=BLUE]vlax-invoke[/color] stm '[color=BLUE]close[/color])
               )
           )
           ([color=BLUE]if[/color] ([color=BLUE]=[/color] 'vla-object ([color=BLUE]type[/color] stm))
               ([color=BLUE]vlax-release-object[/color] stm)
           )
           ([color=BLUE]if[/color] ([color=BLUE]=[/color] 'vla-object ([color=BLUE]type[/color] fso))
               ([color=BLUE]vlax-release-object[/color] fso)
           )
           ([color=BLUE]findfile[/color] txt)
       )
   )
)
([color=BLUE]vl-load-com[/color]) ([color=BLUE]princ[/color])

Test program:

([color=BLUE]defun[/color] c:test ( )
   (nullchartest [color=MAROON]"line-text"[/color] ([color=BLUE]vl-filename-mktemp[/color] [color=MAROON]"test"[/color] ([color=BLUE]getvar[/color] 'dwgprefix) [color=MAROON]".txt"[/color]))
)

works perfectly for me

thank you very much

i think its time to donate your website

one more question

i tried to change little bit your function to write more then one line

(defun nullchartest ( str txt / fso stm )
   (if (setq fso (vlax-create-object "scripting.filesystemobject"))
       (progn
           (vl-catch-all-apply
              '(lambda ( )
                   (setq stm (vlax-invoke fso 'createtextfile txt -1 0))
                   (vlax-invoke stm 'write (strcat str (chr 256)))
                   (vlax-invoke stm 'write (strcat "text for line 2" (chr 256)))   ;;;;;changes
                   (vlax-invoke stm 'close)
               )
           )
           (if (= 'vla-object (type stm))
               (vlax-release-object stm)
           )
           (if (= 'vla-object (type fso))
               (vlax-release-object fso)
           )
           (findfile txt)
       )
   )
)

but in results it write only one (first) line, why is that?

ok, topic closed

i figured it out

i forgot about

(vlax-invoke stm 'write (chr 10))  ;;; starting next line

between lines

thanks you all for help

works perfectly for me

thank you very much

i think its time to donate your website

Excellent, I'm glad it works as required.

Thank you also for your kind offer of a donation, I appreciate it

but in results it write only one (first) line, why is that?

As you have gathered, a carriage return & line feed are required for a new line:

;; Null Character Example by Lee Mac 2014-01-14
(defun nullchartest ( txt / fso stm )
   (if (setq fso (vlax-create-object "scripting.filesystemobject"))
       (progn
           (vl-catch-all-apply
              '(lambda ( )
                   (setq stm (vlax-invoke fso 'createtextfile txt -1 0))
                   (vlax-invoke stm 'write
                       (strcat
                           "This is line 1"     (chr 256)
                           "\r\nThis is line 2" (chr 256)
                       )
                   )
                   (vlax-invoke stm 'close)
               )
           )
           (if (= 'vla-object (type stm))
               (vlax-release-object stm)
           )
           (if (= 'vla-object (type fso))
               (vlax-release-object fso)
           )
           (findfile txt)
       )
   )
)